The British radioed their base calling for air support but could not tell whether the message got through.

Our source said: “The SAS thought they had seen their last day.

“They made a pact that they wouldn’t be taken alive and vowed to fight to the death.

“Capture would mean torture and a filmed execution and they weren’t prepared to let that happen.

“They made every bullet count and when they ran low on ammo they waited for the jihadis to get close enough so they could be killed with grenades or using rifles as clubs – that was when one of the SAS managed to kill a man with a spade.”

(Image: ALAMY)

Just as they thought their time was up, two US Apache helicopter gunships appeared, forcing the insurgents to withdraw.

A US Chinook then came in and rescued them. By the time they arrived half the SAS team had no ammunition left.

Both the Taliban and ISIS have gained ground in Afghanistan but they view each other as enemies.

ISIS attacks have been on the rise in recent weeks and are now seen as the main threat to peace in the war-torn country. Hundreds of fighters are believed to have moved in from Syria and Iraq.

A source said the situation was so bleak in Afghanistan that the number of SAS troops will be doubled in the next few weeks to around 100 men.

The UK has around 500 troops in the capital Kabul but they are not involved in ground combat. The Ministry of Defence does not comment on special forces operations.